flybywire in the uk the caa only stipulates the ratio number of crew:50 pax seats (unfilled or filled, or part thereof) and that where a pax is sat if there is no attendant then they must be briefed on how to open it. anything above this number is company discretion. contractflygal you are quite correct, 50 pax 1 attendant, 51 and you would need two
there has been a special amendment by caa and jarops: that on any inbound sector a flight may operate one below legal minimum (not company policy minimum) if the pax figure is reduced accordingly as this is deemed a rescue flight.
eg: a 767 - 300 (312 config) min crew is 7,
a crew member goes sick downroute and has to be offloaded,
the pax figure must be reduced to 300 but the flight may operate with only 6 crew.